Printing roller etching machine of the spray type



Dec. 10, 1963 J. BOCK ETAL 3,113,901

PRINTING-ROLLER ETCHING MACHINE OF THE SPRAY TYPE Filed Dec. 27, 1957 8 Sheets-Sheet 1 INVENTORS JdaRGEN BOCK EUGENE v HARTMAN PHILIP A. TATUSKO Ma W ATTORNEY Dec. 10, 1963 J. BOCK ETAL 3,113,901

PRINTING-ROLLER ETCHING MACHINE OF THE SPRAY TYPE Filed Dec. 27, 1957 8 Sheets-Sheet 2 '30 INVENTORS 3b JDRGEN BOCK EUGENE v. HARTMAN 2 PHILIP A. TATUSKO ATTORNEY Dec. 10, 1963 J. BOCK ETAL 3,113,901

PRINTING-ROLLER ETCHING MACHINE OF THE span TYPE Filed Dec. 27, 1957 a Sheets-Sheet 5 UUUUUUUUU INVENTORS JRGEN BOCK EUGENE V. HARTMAN FG. 3 0 BY :fTATUSKO ATTORN EY Dec. 10, 1963 J. BOCK ETAL PRINTING-ROLLER ETCHING MACHINE OF THE SPRAY TYPE 8 Sheets-Sheet 4 Filed Dec. 27, 1957 INVENTQRS JQRGEN BOCK N Am S m T A Y v.1 f m E H n L Gll uH W A EP 07 B FlG.3b

Dec. 10, 1963 J. BOCK ETAL 3,113,901

PRINTING-ROLLER ETCHING MACHINE OF THE SPRAY TYPE 8 Sheets-Sheet 5 Filed Dec. 2'7, 1957 wdE INVENTORS JRGEN BOCK EUGENE V. HARTMAN PHlLiP A. TATUSKO BY f 9.10. ATTORNEY Dec. 10, 1963 J. soc ETAL r PRINTING-ROLLER ETCHING MACHINE OF THE SPRAY TYPE Filed Dec. 27, 1957 8 Sheets-Sheet 6 n I T i L ATTORNEY FIG.5

s Sheets-Sheet 7 INVENTORS JRGEN BOCK EUGENE v. HARTMAN PHILIP A. TATUSKO BY 9 W ATTORNEY J. BOCK ETAL PRINTING-ROLLER ETCHING MACHINE OF THE SPRAY TYPE Dec. 10, 1963 Filed Dec. 27, 1957 PRIN' 1 INGROLLER ETCHING MACHINE OF THE SPRAY TYPE Filed Dec. 27, 1957 Dec. 10, 1963 J. BOCK ETAL 8 Sheets-Sheet 8 INVENTORS JRGEN BOCK suczuz v. HARTMAN PHILIP A. TATUSKO 21w,

ATTORNEY United States Patent Office 3,ll3,%l Patented Dec. 10, 1963 3,1133% PRlNTllNG Rfi'll-Elii Eli UHHNG MAQHENE 6i THE TYPE Eurgen heel; and Eugene V. Hartman, Endicett, and Philip A. Tatuslro, Endwell, NHL, to inter national Business Machines @orporation, New Yorlr, N.Y., a corporation oi; New Yuri:

Filed Dec. 27, 19537, Ser. No. 765,535 El (Ql. 156 345} This invention relates to machines for etching metal. It has a more specific relation to an improved machine for producing a relief in the surface of a metal plate, such as magnesium or the like which is soluble in an aqueous acid solution, for the purpose of bringing in relief type characters in making printing plates.

In the conventional method of making a metal printing surface, as in making a photoengraving of an acidsoluble metal such as magnesium, zinc, and their alloys, a light sensitive coating or enamel is applied to the metal surface which is usually flat or cylindrical. The coated surface is exposed to light through a negative having an image therein so as to produce a corresponding image in the coating. The exposed coated surface is developed forming an acid resistant coating in the form of the image produced by the exposure. The acid resistant coating, which is referred to as a resist, is usually further hardened as by a hardening treatment which increases its resistance to the etching acid. The surface of the metal bearing the so prepared resist is then subjected to etching by an acid.

The etching is usually carried out with nitric acid suitably diluted with Water, the acid solution being usually splashed or otherwise impinged against the object. The acid solution attacks the bare portions of the metal, that is, the portions of the object denuded of the light sensitive material in the developing operation. The rest or" the metal surface is protected by the resist from direct attack by the acid which does not penetrate the resist. As the etching proceeds, metal from the bare portions of the object dissolves away, leaving the adjacent image in vertical relief. As soon as a moderate depth of etch is made in this way, attack by the acid in a lateral direction on the metal supporting the acid-resisting image becomes noticeable and the resist may be undercut slightly around its edges.

It is recognized in the art that undercutting of the type walls is very objectionable because the shoulders or side cuts in the side walls of the type provide recesses in which dirt and inl:- may lodge and cause fuzzy or blurred impressions when printing is effected from such etched printing plates. The elimination of such undercutting has been the object of improvements disclosed the past among which are those disclosed in Patents Nos. 2,640,- 673, 2,640,674, 2,640,675, 2,649,676 and 2,640,677. In general, the specifications of these patents specify that the improvements are predicated upon the discovery that by including in the acid etching bath, and impinging the bath composition against the object to be etched, certain agents which produce a removable acid resistant film that exerts a controlling effect on the dissolving action of the acid, the dissolving action of the acid normal to the surface of the work is not adversely affected while the dissolving action laterally, that is, in a direction which tends to dissolve away metal in relief and undercut the resist, is substantially reduced.

The solution recommended, and preferably employed in the present machine consists of the metal dissolving nitric acid etching solution in a mixture of diethylbenzene and Aerosol, which two latter are herein the coating or film ingredients for protection against undercutting of the type walls. While this solution has been found efficient for rapidly etching flat magnesium plates the utilization of the ctchant when printing cylinders were processed by prior art machines did not produce the desired results, and undercutting of the type walls was prominent to an objectionable extent.

To this end, a machine which is disclosed in applicants copending application, Serial No. 671,233, filed July 11, 1957, now abandoned, has been developed to improve the application of the etchant with the protective film to the printing cylinder. Said machine utilizes a nozzle spraying system which discharges a mist-like spray on the printing cylinder perpendicularly to the surface. The force of the spray penetrates the film to reach and etch the metal. The perpendicular emission of the spray overcomes, to a great extent, the undercutting along radial lines. This machine, as in the present machine, provided for both continuous rotation of the printing cylinder and axial reciprocation, both of such movements combining to spread the protective film over the surface of the metal and build up the film protection along axial lines to give the side walls along axial lines additional film protection.

In the machine of the above identified application the printing cylinder Was mouned isolated from and above the tank holding the etching solution, and therefore was not submerged in the etching solution in the tank. This allowed the natural force of gravity to drain off the etching solution into the tank, and with the result that the draining oil of the film from the cylinder provided relatively less side-wall protection along radial lines.

In the machine of the above identified application, the horizontal rotation of the cylinder carried the protective film around the surface of the cylinder which caused the film to build up more on axial lines of the cylinder than on radial lines. This gave the side-walls of the axial lines somewhat more protection against undercutting so that they did not etch the cylinder laterally as much as along radial lines, which received less side-wall protection due to the natural force of gravity, allowing the Aerosol-diethylbenzene film to drain off more readily.

irrespective of the above disadvantages admirable results were obtained from this improved machine and printing cylinders were produced in a taster time and contained relatively little lateral or radial undercutting of the type. To the end that further improvements might be made, further research and development resulted in an improved machine shown in the present application and which discloses an improved etching applying means overcoming all objections to the prior machine.

it is, therefore, the main object of the present invention to devise a metal etching machine of the spray type which utilizes a film protective ingredient and apply the etcliant in an improved manner to the printing cylinder so that undercutting of the type is equally prevented along radial and axial lines.

A still further object of the present invention is to provide an improved etchant applying means comprising a spray nozzle system for directing etchant sprays perpendicularly to the cylinder surface in combination with means to retain the cylinder partially submerged in said etchant whereby gravity drain-off or" prior machines is prevented and the protective film or" the etchant is more evenly distributed as the cylinder is rotated.

A still further object is to provide a spray nozzle systern which directs etchant fluid to the printing surface at the point where the printing surface emerges from the bath in which the printing cylinder is immersed and rotates therein, whereby the amount of side flow after impingement is reduced.

Other incidental and also relatively important objects will be apparent as the improved etclrant applying means is understood. As the description is developed such improved construction and improved results will be explained in more detail.

Other objects of the invention will be pointed out in the following description and claims and illustrated in the accompanying drawings, which disclose, by way of example, the principle of the invention and the best mode, which has been contemplated, of applying that principle.

In the drawings:

FIG. 1 is a perspective view of the assembled etching machine embodying the present improvements.

FIG. 2 is an elevational view of the left end of the machine, as viewed in FIG. 1.

FIGS. 3 and 3b are elevationail views of the rear of the machine taken on the line 3a, 311) of FIG. 2.

FIG. 4 is a sectional view taken through the tank at the rear on the line 4-4 of FIG. 2 to show the relationship of the nozzle spray devices and the printing cylinder rotating land axially shifting means.

. FIG. 5 is a sectional view taken on the irregular section line 5-5 of FIG. 4.

FIG. 6 is a transverse sectional view taken on the section line 6-6 of FIG. 4, but upon an enlarged scale.

FIG. 7 is a detail view showing principally the printing cylinder rotating means.

FIG. 8 is a detail view of the care which effects the axial shifting of the printing cylinder during its rot-a- Assembled M achine The external appearance of the assembled machine is best shown in FIG. 1 as it is viewed by an operator eniploying it for etching printing cylinders. However, as will also appear in other views, the framework of the machine comprises vertical and horizontal struts lit which are bolted together to carry suitable base members, brackets, etc. for supporting the machine urn'ts. The machine is preferably open at the rear for ventilation and service purposes but is covered at the front and sides for better appearance bystainless steel panels ill and 12. The panels at the ends or sides may also be removable to give, as shown in FIG. 1, access to the interior units for the purpose of ins ection and adjustment. It is preferable to use stainless steel for the panels because it is resistive to the ac-idulous etching bath employed herein.

The top of the cabinet is covered by a stainless steel cover 1-3 having a work surface or apron l4 and a relatively deep sink 155' over which is placed "a mixing [faucet assembly 16. At the left of the sink there is disposed a hinged cover plate 17 which is over an opening in the apron 14 registering with the tank to be subsequently de scribed. To the rear of the hinged cover plate 117 there is fixedly secured a panel 18 carrying a main line power switch button 19, and three motor drive initiating buttons 20, one for the circulating motor and pump, and second for the motor for rotating and axially reciprocating the printing cylinder, and the third for the spray motor and pump.

In addition, there is' provided, on the panel 18, a pressure gauge 25, a settable electric timer 26, a temperature gauge 27, and a pressure regulating knob 72. The electric timer 26 is in series with the spray motor, thus making it possible to select the etching period and have the motor shut oii automatically after this period has elapsed. During this period the spray motor reverses its rotation. The pressure gauge 25 indicates thepressure of the fluid directed to the spray nozzles, and the thermometer 2 7 indicates the temperature of the etching bath.

In FIG. 3a there is shown the commercim device known as the Electropulse 28 which has suitable manual adjustments and electrical controls to the spray motor to reverse its direction, and after unequal periods, or unequal numbers' of rotation in the two directions.

Etching Tank The tank 30 which contains the etching fluid is a sub stantially square metal box formed of stainless steel "1 ingredients of the etching fluid and said tank is fully pen at the top and is covered by the hinged cover '7.

There is located in the tank above the level of the solution the drive for rotating the arbor carrying a printing cylinder to be etched. The spray p ump receives the fluid from the bottom of the tank and discharges it above the fluid level to the spray nozzles in the tank. The circulating pump likewise takes fluid from the bottom of the tank and discharges it back into the tank to keep the ingredients properly mixed.

There is also submerged in the tank a coil 25 (FIGS. 2 and 4) connected to the temperature gauge 27 having a temperature sensitive bulb which controls the refrigeration unit RU. (FIG. 2) to keep the temperature of the etchant within a desired range. The etching tank is also provided with a cooling coil 36 (FlGS. 2 and 4) located at the bottom of the tank and also submerged in the etchant.

For communication between these different units there are a plurality of tubes and connectors and a drive shaft passing through a wall of the tank, most of them passing through the back wall of the tank with suitable bushings to prevent leakage of the fluid.

Refrigeration Unit The refrigeration unit RU. is a commercial unit which is mounted at the base of the machine at the rear, as shown in FIGS. 3a and 3b. The cooling coil 36 is connected to the refrigerating unit by tubes 37. The refrigerating unit does not operate constantly but is called into operation according to the temperature of the etching bath. To this end the temperature gau e 27 has a temperature responsive switch which is closed when the temperature exceeds the desired range to connect the line side to the motor of the refrigeration unit. This is an obvious and well known type of control and deemed not necessary to disclose it herein to understand the present invention.

In the etching process the acidulous bath generates heat and resultant fumes which it is necessary to reduce and for temperature control the above described refrigeration unit is preferably employed.

Circulating Motor and Pump Before the machine is set into operation the tank is filled with the etching fluid of a composition to be described to the desired level. The fluid which has been previously mixed according to the desired composition and brought to the desired range of temperature may be poured from a pail into the tank or pumped therein.

The combined circulating motor and pump may then be set into operation. Said combination motor and pump is mounted upon the bottom base plate 3% beneath the tank 3d and consists of a motor 4t? (FIGS. 1, 2, 3b) and a directly connected driven fluid pump 41. The motor is set into operation by the depression of the button 2% (FIG. 1) on the panel it"; marked Circpump. From the suction side 43 of the hydraulic fluid pump 4-1 there is a duct or tube 44 having an opening to the bottom of the tank (see FIG. 4). The fluid flows by the gravity from the bottom of the tank to the suction side of the pump, and said pump forces it back under pressure through a tube as which passes through the back wall of the tank. The tube 46 is connected to a tube 47 which is within the tank and bent downwardly to terminate in the bath so as to discharge the iluid with a forceful swirling motion. This is a relatively important operation in the process since the protective film of the present etching fluid may separate out into its respective components unless the fluid is kept in constant agitation and motion.

- The circulating motor and pump work independently of all the other units and may or may not be called into operation, depending upon the behavior of the fluid during the etching operation.

a.e which is not subject to the corrosive action of the Etching Bath Nitric acid 10.5%. Diethylbenzene 7.0%.

Aerosol (trademark) .40%.

Gelatin From 50 to 125 of .l%

stock solution. All in a water solution.

The above solution in combination with a special machine provides for rapidly etching flat magnesium plates to a depth of .015 "-018" without any substantial undercutting. However, this solution is not efiective for rapidly etching magnesium printing cylinders to a comparable or greater depth without any undercutting. This is especially true for cylinders of small diameter and consequently high curvature of the printing surface. In the present ma chine a modification of the solution together with a novel means for impinging the solution against the printing cylinder and efiecting concurrently its rotation and axial reciprocation will effect etching of a cylinder 2%" diameter or larger to a depth of .018".021 in one step without undercutting.

One improvement consists in modification of the above solution by the complete exclusion or" one ingredient, gelatin. This is an important improvement as the gelatin balance in the flat plate bath is very critical. The gelatin deteriorates and the rate of deterioration is governed by a time factor. By exclusion of gelatin a better control of the etch can be obtained. The rate of etch in the present machine is governed only by the number of cylinders processed in a bath. The time elapsed betweenetches has no effect on the result.

Aside from the modification of the solution, several mechanical improvements are incorporated in the present machine. The Aerosol ingredient combined with diethylbenzene forms a protective film which protects the side Walls from etching. In the present machine the solution is directed as a continuous forceful spray normal to and against the rotating cylinder and is effected by a motor, a hydraulic pump, and a spray nozzle system. The directing of the acid solution against the cylinder with force and perpendicularly with respect to the axis of rotation causes the acid to penetrate the film and effect the etching operation according to the acid resist on the surface.

The protective film gives the sidewalls of the etched type along radial lines the desired protection against undercutting. Means is also provided to effect the rotation f the cylinder which carries the film around the periphery of the cylinder and build it up along axial lines. The movement of the film in this direction prevents the undercutting in a lateral, or axial direction.

In addition to said film protection, the amount of etchant impinging the cylinder is regulated by a pressure controlling valve so that after said etchant has once been in contact with the cylinder, and lost some of its initial velocity, it is no longer capable of etching.

Spray Motor and Pump When the tank cover has been closed and the electrical timer has been set for the selected period of operation the depression of the switch button 18 on the panel marked Spray (see FIG. 1) will cause the spray motor 58 to be set into operation. The spray motor 50 (FIG. 2) is mounted on the base 33 and drives a hydraulic fluid pump 51 (FIGS. 2 and 3b), the suction side of the pump receiving fluid fed by gravity from the bottom of the tank 30 by a tube 52, one end of which opens into the bottom wall of the tank (see Phil. 4) and the other is connected by a compression fitting 53 to the suction side to the pump. The pump discharges the fluid at its maximum pressure capacity through a strainer 54 (FIGS. 2 and 3b) and a tube 55 which is connected at one end to the inlet of a three-outlet junction fitting 56. The fluid discharges at one outlet 57 of said fitting 56 to a tube 58 terminating at a fitting 59 which leads the fluid discharge through a tube 60 to a T 61 (FIGS. 2 and 5) leading to the spray nozzle system to be described later. The etching fluid also discharges at a second outlet 62 (FIGS. 2 and 3b) through a tube 63 connected to the pressure gauge 25 mounted on the panel. This will indicate at all times the pressure of the etching fluid. The third outlet 65 (FIGS. 2 and 3b) of the junction fitting 56 is connected by a short tube 66 to a gate valve 6'7 which is open more or less to enable the etching solution to be lay-passed by a tube 68 to a bushing fitting 6? in the back Wall of the tank leading to a tube 79 (FIGS. 5 and 6) within the tank. Said tube 7 0 is bent downwardly as shown in FIG. 6 to terminate and open in the bath to stir the discharge in the solution to aid in the agitation of the etchant.

The adjustment of the shaft of the gate valve 67 to permit the fluid to be directly discharged into the bath and by-pass the nozzles is conveniently effected by a retatable knob 72 (FIG. 1) mounted on the control panel 18. By bypassing the discharge fluid around the nozzles, it is possible to adjust the pressure of the etching fluid supplied to the nozzles and meter it within very close limits. Thus, the force of the sprayed etchant to produce the desired depth of etch without radial and lateral undercutting can be controlled.

Spray Nozzles The spray nozzle arrangement now to be described receives the etching fluid from the spray pump at a defnite pressure and impinges two opposing sprays perpendicularly against the opposite peripheral. surfaces of the rotating printing cylinder. The force of the spray causes the etching acid to pass through the protective film and etch the metal, the radial direction of the spray preventing undercutting in a radial direction, and producing straight or steeply sloping radial walls for the etched type.

Attached to the top of the front and rear walls of the tank are respective fluid manifolds 73 and 74 (FIGS. 5 and 6). More specifically each manifold consists of two parts 75 and 76 fastened together by screws 77. Each part is machined so as to form in combination an etch ant fluid reservoir 78, it being understood that the reservoir is closed at its ends. Each manifold is secured to the related tank wall by screws 7? so that the manifolds are midway of the tank. As best shown in FIG. 6, the manifolds are high up in the tank and just beneath the cover 17.

From the sides of the T 61 there are outlet tubes 80 and 81 which through a related elbow 32 have an entrance into the reservoir 78 of the respective manifold 73, 74. When each manifold is completely filled it is built up to the pressure indicated on the pressure gauge and this causes the fluid to be discharged through the nozzles mounted on the top of each manifold as will now be described.

Each manifold has a row of four nozzles 85 screwed into the manifold so as to open into the reservoir 78 and the nozzles have their diffusion slots E56 aimed to direct sprays of the etchant in overlapping fashion to the center of the shaft of the printing cylinder Till, along the spray lines 88 (see FIG. 6). The opposing overlapping fan-like sprays from each of the two rows of nozzles are directed to opposite peripheral surfaces of the rotating 7 printing cylinder to make certain that if one nozzle does not impinge the spray against a certain area of the printing cylinder, another nozzle or nozzles will take care of this inadequacy.

' Printing Cylinder Rotating Means When the button 255 1G. 1) on the operating panel 18 marked Drive is depressed the power circuit to the drive motor llltl (FIGS. 1 and 2) is completed and a drive mechanism operated by the motor is set into operation to impart both a rotary motion and axial motion to the printing cylinder ltlll (FIG. 4). The electrical circuits for initiating the operation of the drive motor 1% and the other motors are not shown since they are well known.

The drive motor 1% (MG. 1) is mounted upon the bottom base plate 38 of the machine and through a speed reduction mechanism 102 rotates a pulley Elli. The pulley 163 (FIG. 2) rotates a pulley MM through a belt MP5. The pulley we is secured to one end of a shaft 1% (FIG. 7) journaled in a casting Hi3, and the free end of the shaft 166 has secured to it a wide gear 109. The casting MP8 is the main support for the drive for the printing cylinder which is located outsideof the tank 3%. Said casting has three integral feet lit fill, 112 (FIG. 7) which are fastened by respective screws 113 to the left side wall (as viewed in FIG. 1) of the etchant tank.

Iournaled in the bracket res outside of the tank is a rotatable and axially shiftable shaft 115 to which is fixed a gear 116 which meshes with the gear 109. Gear 1159 is wider than the inter-meshing gear 116, in order to continuously retain the engagement of gears ill? and 116 in the different relative positions of the gear 116 and shaft 115. The left end of the shaft 115 passes through the tank 3% and is supported by the left side wall of the tank by a support described as follows: A cylindrical hollow bearing 119 passes through a hole 12% in the tank wall andwithin the tank it has an annular flange 121 bearing against the inside Wall of the tank and an intermediate ring gasket 122. Outside of the tank wall there is provided a tightening nut 123 engaging the threaded portion 124 of the cylindrical bearing. Tightening of the nut 123 places compression on the gasket 122 and securely attaches the cylindrical bearing 119 to the tank wall in a leak proof manner. The shaft 115 passes through the center of the cylindrical bearing 119 and to furnish the shaft 115 with a leak-proof seal, there is fitted over the shaft 115 a series of five lubricated rings 125 which alternate with separating washers 126 and an end ring 127. A compression nut 128 threaded on the threaded portion 129 of the cylindrical bearing 119 compresses the assembly together and against an annular ring 130 of the cylindrical bearing 119 outside. of the tank. The above construction provides a sealed lubricating bearing for the shaft 115 where it passes through the left side wall of the tank 30. I

The left end of the shaft 115, which is in the etching tank 3%, has attached thereto a gear I135 (see FIG. 4) on each side of which there is attached a thrust side plate 136 of greater diameter than the outside periphery of the .gear.

To the right tank wall which is opposite to the left tank Wall that the above described drive mechanism passes through, there is attached an upstanding bracket Mil having a semi-circular shaft bearing notch Ml. Similarly, the left side of the tank where the aforesaid drive mechanism projects through there is secured a bracket 142 having a semi-circular shaft bearing notch 143, both notches being lined with a low friction, acid resistant bearing material.

The printing cylinder arbor support comprises several parts which, when assembled together, support the printing cylinder 161, and in such manner that the assembly may be made before insertion in the tank of the machine for processing, then easily inserted in the machine on the Error 144 of the notches 141 and 143 of respective brackets Mil, 14?. and after processing the cylinder and arbor support may be withdrawn from the machine for washing, etc. it comprises a lefthand annular plate 145 (Fl-G. 7) attached to the lefthand arbor shaft 147 by a set screw Similarly, a right hand annular plate 15-9 is secured to the righthand arbor shaft E51 by a set screw (not shown). Plates 146- and 150 each have shoulders or annular flanges 152 over 'which the printing cylinder ltl ll is placed. The external periphery of the shoulders of the annular plates 146 35 conforms to the inside diameter of the printing cylinder Jill-1 and being the same size said printing cylinder 1G1 firmly fits on both support ing plates 146 and 151). As the printing cylinder fill is so assembled a threaded end 153 of the leftnand arbor shaft 147 is manually screwed into the internal threaded hole lS-i of the annular plate 15% to fit the printing cylinder 18 1 tightly between plates 2.5%, 151. A ring gasket 155 of a compression type assists in making a tight un tary assembly. To facilitate handling of the assembled printing cylinder arbor support and assist in the screwing of the arbor shaft i 27 into the annular plate 156', each shaft 14-7 and rail. carries respective knurled cylinders E56, 157. After the assembly has been made as shown in FIG. 7, the assembled printing cylinder arbor support carrying the printing cylinder 36 1 to be etched is placed in the etching tank with the shafts. 147 and 15-1 fitting in the semi-circular bearing notches 141, 143 of the respective brackets 14%, 142.. When so placed and journaled a gear 153 (see PlG. 4) secured to the end of the shaft 151 meshes with the gear 135 and is caused to fit in between the thrust side plates 135 of gear 135. When this gear drive relationship is made, starting of the drive motor Hill will rotate the printing cylinder lit-l after which the spray motor 46 will be started to cause the spray pump d ll to spray the etching solution upon the peripheral surface of the now rotating printing cylinder Mil. During this rotation it is desirable to axially reciprocate the printing cylinder fill to cause the uniform application of the etchantand to spread the film along an axial direction and more evenly over the periphery.

Means to Effect Axial Reciprocation of Printing Cylinder As best shown in FIGS. 4 and 7 there is secured to the casting or bracket 188 by screws 159 a bracket 169. A circular disk 262 fits in a hole in the underside of the bracket 16% and said disk has an integral cam follower projection 161 (see also FIG. 8). Fixed to the end of shaft 115 is a cam cylinder 163 formed with a continuous cam slot 154 around its periphery in which fits said cam follower projection fo While not shown the underside of the cam follower projection 15?. is circular to conform to the circumference of the cylindrical cam at the bottom of the cam slot 164. The cam slot 164 is continuous and has one complete righthand thread and one complete lefthand thread having a common point of intersection and joining of the ends of the cam race. The effect of this cam slot 164 and its engagement by the stationary cam follower 161 is to' move shaft 115 and the printing cylinder fill axially in one direction and then the other as sai shaft 16 .5 is rotated. During this operation the reciprocable axial movement of thrust gear 135 carried by shaft 115 shifts the gear 153, shaft 151 and printing cylinder fill similarly and the narrow gear 116 slides back and forth over the gear 169 Without, however, effecting a denies-hing of the teeth of the gears.

Mode of Etching Operation The present invention embodies an improved mordant In the present machine and the one shown in the above identified application, upon impingement of the spray on the surface of the cylinder, the acid etches the cylinder and the Aerosol'diethylbenzene combination forms an acid resisting film which protects the sidewalls from etching. In the machine of the above identified application the horizontal rotation of the cylinder carried this film around the cylinder which caused this film to build up more on the axial lines of the cylinder than on the radial lines. This gave the sidewalls of the axial lines somewhat more protection so they did not etch the cylinder laterally as much as along radial lines which received less sidewall protection due to the natural force of gravity allowing the Aerosol-diethylbenzene film to drain off more readily. This necessitated a closer control of the etching to maintain a balance between the undercutting of the radial lines and the shouldering oil of the axial lines.

The present improvement has been designed and proven to give more latitude and better control in the etching. To this end there is provided a tray 165 (FIGS. and 6) which extends almost the width of the tank and is supported by the brackets 14% and M l. When the printing cylinder is in the brackets 14%, 14-1 the level of the mordant in the tray is above the horizontal center line of the printing cylinder. Each of the rows of spray a tomizing nozzles 35 is aimed at the center of the cylinder so that the spray impinges on the cylinder at the level of the mordant and fills the tray 165 to the desired level.

Since more than half of the cylinder is submerged, the quantity of mordant is equally applied to all surfaces of the cylinder. There is no gravity drain-off directly from the cylinder when submerged so that when a surface portion of the cylinder emerges from the mordant, the Aerosol-diethylbenzene film has been equally applied over the entire surface of the cylinder. The impingement of the etching acid from the nozzles 85 causes etching of the surface which is equal for both axial and radial lines. Rotating the printing cylinder in the mordant does not cause any appreciable etching as the cylinder receives a protective film from the Aerosol-diethylbenzene combination and it takes the force of the spray to break through this film to cause etching.

A further advantage is obtained by this etching applying arrangement in the reduction of the amount of mordant hitting the sidewalls of characters being etched. When the etching mord-ant is brought up from the bottom such as from D (see FIG. 6), the mordant is free to go at right angles in both directions after hitting the cylinder. This right angle deflection would be sufiicient to cause some lateral etching of the sidewalls. At point E the two right angle deflections would meet and be deflected upwards causing additional etching. When the nozzles are moved so as to impinge at the mordan-t level,

lit

the acid is deflected upwards towards F. The mass of the mordant at the cylinder level absorbs the mordant that is deflected downwards, therefore, half of the lateral etching caused by the acid coming oil at an angle is eliminated. This makes it possible to obtain better sidewall proteotion and etch to greater depths with less undercutting.

While there have been shown and described and pointed out the fundamental novel features of the invention, it will be understood that various omissions and substitutions and changes in the dorm and details of the device illustrated and in its operation may be made by those skilled in the art, without departing from the spirit of the invention. It is the invention, therefore, to be limited only as indicated by the scope of the following claim.

What is claimed is:

In a machine for spraying and coating a metal printing cylinder surface with a nitrous acid etchant solution containing in admixture therewith ingredients comprising a removable acid resistant film for preventing undercutting of type walls, a tray filled with said etchant solution to a predetermined liquid level, means for axially mounting and submerging the printing cylinder for rotation in said tray with said liquid level slightly above the horizontal axis of the cylinder, at first row of spray nozzles disposed on one side of said cylinder, a second row of spray nozzles disposed on the opposite side of said cylinder, said spray nozzles being provided with diffusion slots to forcibly dispense a thin sheet of overlapping sprays of said etchant solution, means for axially rotating said cylinder past said first and second rows of nozzles, respectively, while submerged to coat the surface of said cylinder uniformly over the entire peripheral surface with said acid resistant film, mounting means for arranging said first row of nozzles at an angle so that the thin spray sheet of etchant therefrom strikes the peripheral surface of said cylinder perpendicularly and slightly below the level of the solution in said tray, and mounting means for arranging said second row of nozzles at an angle so that the thin spray sheet of etchant therefrom strikes the opposite peripheral surface of said cylinder perpendicularly and slightly below the level of the solution in said tray.

References Cited in the file of this patent UNITED STATES PATENTS 2,360,676 Henderson et al. Oct. 17, 1944 2,828,192 Langsfeld Mar. 25, 1958 2,926,076 Guenst Feb. 23, 1960 FOREIGN PATENTS 23,493 Great Britain 1905 6,115 Great Britain 1912 

